Electroluminescent display device having pixel driving

Abstract

An electroluminescent display device comprises subpixels each including a pixel driving circuit driven in accordance with an initialization period, a sampling period and a light emission period. The pixel driving circuit includes a light emitting diode, a driving transistor including a gate connected to a first node, a drain connected to a second node, and a source connected to a third node, a first switching circuit turned on for the initialization period, providing an initialization voltage to the first node and providing a fixed voltage to the third node, a second switching circuit turned on for the sampling period, applying a data voltage to the third node and providing the initialization voltage to an anode of the light emitting diode, and a light emitting control circuit controlled by an emission signal and turned on for the light emission period to provide a high potential voltage to the third node.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of Republic of Korea Patent Application No. 10-2019-0166499 filed on Dec. 13, 2019, which is hereby incorporated by reference in its entirety.BACKGROUNDTechnical Field[0002]The present disclosure relates to an electroluminescent display device comprising a pixel driving circuit, and more particularly, to an electroluminescent display device effective for variable frequency driving.Description of the Related Art[0003]With the advancement of the information technology, the market for a display device which is a connection medium between a user and information has grown. Various types of communications beyond information transfer based on text messages between users are actively ongoing. As the type of information changes, performance of a display device for displaying information has been developed. Therefore, various types of display devices such as an organic light emitting display device, a micro-LED d...

AI Technical Summary

Benefits of technology

[0010]The inventors of the present disclosure have recognized the aforementioned problems and invented an electroluminescent display device comprising a pixel driving circuit, which may reduce non-uniform luminance that may occur during driving of the display panel at a variable frequency, from occurring in the electroluminescent display device to which a driving method through frequency variation is applied

[0011]The present disclosure has been made in view of the above problems, and it is an object of the present disclosure to provide an electroluminescent display device comprising a pixel driving circuit, which may reduce a leakage current of a gate node of a driving transistor.

[0012]It is another object of the present disclosure to provide an electroluminescent display device comprising a pixel driving circuit, which may reduce luminance deterioration of a first frame from occurring during screen switching of a display panel.

[0014]In accordance with an aspect of the present disclosure, the above and other objects can be accomplished by the provision of an electroluminescent display device comprising a plurality of subpixels included in an nth row and each including a pixel driving circuit driven in accordance with an initialization period, a sampling period and a light emission period. In this case, ‘n’ is a natural number. The pixel driving circuit includes a light emitting diode, a driving transistor including a gate connected to a first node, a drain connected to a second node, and a source connected to a third node, a first switching circuit turned on for the initialization period, providing an initialization voltage to the first node and providing a fixed voltage to the third node, a second switching circuit turned on for the sampling period, conducting the first node and the second node, applying a data voltage to the third node and providing the initialization voltage to an anode of the light emitting diode, and a light emitting control circuit controlled by an emission signal and turned on for the light emission period to provide a high potential voltage to the third node and deliver a driving current to the light emitting diode. In this case, a capacitor is connected to the first node and a high potential voltage line to which the high potential voltage is provided. Therefore, luminance deterioration occurring when the electroluminescent display device capable of being driven at a variable frequency is driven at a low speed, may be reduced.

[0017]According to the embodiments of the present disclosure, a fixed voltage is applied to a source of a driving transistor at a step prior to a step of sensing a threshold voltage of the driving transistor among driving steps of the pixel driving circuit, whereby luminance deterioration, which may occur in a first frame during screen switching, may be reduced.

[0018]According to the embodiments of the present disclosure, transistors connected to a gate of the driving transistor may be embodied as N-type transistors, whereby a leakage current, which may occur in the gate of the driving transistor, may be reduced.

Problems solved by technology

Also, if transistors included in a pixel driving circuit are embodied as P-type polysilicon transistors, a leakage current of a gate node of a driving transistor may occur during low-speed driving.

Since occurrence of the leakage current makes a light emitting diode difficult to maintain the same luminance for one frame and increases a data update period, flicker may be seen.

Also, luminance deterioration of a first frame is generated due to hysteresis of the driving transistor during switching from a black screen to a white screen.

Since luminance deterioration of the first frame causes high visibility during low-speed driving, quality of the electroluminescent display device may be deteriorated.

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